Subframe construction for front suspension

ABSTRACT

There is provided a subframe construction for a front suspension that increases the suspension arm attachment strength at the time of front collision. In the subframe construction for a front suspension, comprising a front cross member  1  disposed at the front part of a vehicle body; a rear cross member  3  disposed on the rear side of the front cross member; a pair of right and left subframe bodies  5, 5  for connecting these cross members  1  and  3  to each other, the subframe body  5  having an upper panel  31  and a lower panel  33  forming a hollow portion  35  therebetween; and a rear arm bracket  11  installed to the rear side on the outside in the vehicle width direction of the lower panel  33  constituting the subframe body  5,  the panel shapes of the upper panel  31  and lower panel  33  ranging from the lower panel face on which the rear arm bracket  11  is mounted on the lower panel  33  to the rear side of the lower panel  33  are formed substantially into a spherical shell shape.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a subframe construction for afront suspension.

[0003] 2. Description of the Related Art

[0004] As shown in FIG. 13, a subframe body 101 of a conventionalsubframe for holding a front suspension is constructed so that an upperpanel 103 having a chevron shape in cross section and a lower panel 105having an inverted chevron shape in cross section are joined to eachother so as to form a hollow portion 107 between the panels 103 and 105.On a face 105 on the outside in the vehicle width direction of the lowerpanel 105, there is disposed a suspension arm mounting bracket 109formed by bending a plate material substantially into a U shape. Asshown in the figure, in front of and behind the attachment portion ofthe suspension arm mounting bracket 109, work spaces are secured toperform bolt tightening work when a suspension arm is installed to thebracket 109.

[0005] In this case, in a case where stiffness in the longitudinaldirection of the bracket 109 is not secured sufficiently, when an impactforce is applied to a vehicle from the front side, it is difficult toabsorb impact energy caused by a load transmitted from a tire.Therefore, stiffness of a degree such as to be capable of absorbing theimpact energy must be secured by sufficiently increasing the platethickness of the bracket 109, which results in an increase in vehicleweight, leading to an increase in cost.

[0006] Also, since the bracket 109 is disposed on the side face of thesubframe body 101, the length of the suspension arm cannot be increased.

SUMMARY OF THE INVENTION

[0007] The present invention has been made to solve the above problems,and accordingly an object thereof is to provide a subframe constructionfor a front suspension that increases the suspension arm attachmentstrength at the time of front collision.

[0008] To achieve the above object, the present invention provides asubframe construction for a front suspension, comprising a front crossmember disposed in the vehicle width direction at the front part of avehicle body; a rear cross member disposed in the vehicle widthdirection on the rear side of the front cross member; a pair of rightand left subframe bodies for connecting these cross members to eachother, the subframe body having an upper panel and a lower panel forminga hollow portion therebetween; and a suspension arm mounting memberinstalled to the rear side on the outside in the vehicle width directionof the lower panel constituting the subframe body, wherein the panelshapes of the upper panel and lower panel ranging from the lower panelface on which the suspension arm mounting member is mounted on the lowerpanel to the rear side of the lower panel are formed substantially intoa spherical shell shape.

[0009] The above-described spherical shell shape means a sphericalsurface shape drawn with the suspension arm mounting member being thecenter, being a shape which is formed by dividing a hemisphere openingdownward into about one-fourth and whose front side and outside in thevehicle width direction are open. This spherical shell shape is notlimited to a completely spherical shape, and may be a somewhat curvedshape such as an egg shape. To the suspension arm mounting member isinstalled a suspension arm, and the suspension arm is provided with awheel and a tire. When an impact force is applied to a vehicle from thefront side, the front tire is subjected to an impact load, and thisimpact load is transmitted from the suspension arm to the mounting faceof the subframe body via the suspension arm mounting member. Therefore,by forming this mounting face substantially into a spherical shellshape, the impact load imposed on the mounting face is distributeduniformly, so that the strength of the subframe body increases. As aresult, even when an impact force is applied to the vehicle, thesubframe body is less damaged.

[0010] Also, in one mode of the present invention, a lower side portionof the mounting face of the lower panel formed substantially into aspherical shell shape is depressed toward the inside in the vehiclewidth direction, and the suspension arm mounting member is installed onthe depressed panel face.

[0011] Further, in another mode of the present invention, thelongitudinal position of the panel face on which the suspension armmounting member is installed is substantially aligned with the positionof the rear cross member.

[0012] In still another mode of the present invention, the suspensionarm mounting member and the panel face of the lower panel located on therear side of the mounting member are connected to each other by a firstreinforcing member. Also, in still another mode of the presentinvention, the panel face of the lower panel located on the rear side ofthe suspension arm mounting member and the upper panel are connectedlongitudinally to each other by a second reinforcing member.

[0013] Therefore, the impact load imposed on the suspension arm mountingmember is also distributed to the first and second reinforcing members,so that the strength of the subframe body is further increased.

[0014] Specifically, a component force in the vehicle width direction ofthe load imposed on the suspension arm mounting member is taken by therear cross member, and a component force in the vehicle longitudinaldirection of the load can be taken by the lower panel and further theupper panel via the first and second reinforcing members. Further, sincethe upper panel and lower panel between the rear cross member and thesecond reinforcing member are formed substantially into a sphericalshell shape, the load can be distributed uniformly.

[0015] In still another mode of the present invention, as the firstreinforcing member, a rod-like or plate-like tie down hook can be used.

[0016] Although the tie down hook is usually used to fix a vehicle atthe time of transportation of vehicle, the tie down hook can be usedeffectively as the first reinforcing member.

[0017] In still another mode of the present invention, as the secondreinforcing member, a cylindrical reinforcing pipe can be used. Thecylindrical reinforcing pipe is arranged so that the axis thereof issubstantially aligned with the centers of the mounting holes in the reararm bracket.

[0018] The reinforcing pipe is formed so as to have an inside diametersuch that an attaching bolt, a washer, and a tool such as a socketwrench can pass through.

[0019] In the subframe construction for a front suspension in accordancewith the present invention, comprising a front cross member disposed inthe vehicle width direction at the front part of a vehicle body; a rearcross member disposed in the vehicle width direction on the rear side ofthe front cross member; a pair of right and left subframe bodies forconnecting these cross members to each other, the subframe body havingan upper panel and a lower panel forming a hollow portion therebetween;and a suspension arm mounting member installed to the rear side on theoutside in the vehicle width direction of the lower panel constitutingthe subframe body, the panel shapes of the upper panel and lower panelranging from the lower panel face on which the suspension arm mountingmember is mounted on the lower panel to the rear side of the lower panelare formed substantially into a spherical shell shape. Therefore, acomponent force in the vehicle width direction of the load imposed onthe suspension arm mounting member is taken by the rear cross member,and a component force in the vehicle longitudinal direction of the loadcan be taken by the lower panel and further the upper panel via thefirst and second reinforcing members. Further, since the upper panel andlower panel are formed substantially into a spherical shell shape, theimpact load imposed on the mounting face is distributed uniformly.Therefore, even when an impact force is applied to the vehicle, thesubframe body is less damaged.

[0020] Also, according to one mode of the present invention, a lowerside portion of the mounting face of the lower panel formedsubstantially into a spherical shell shape is depressed toward theinside in the vehicle width direction, and the suspension arm mountingmember is installed on the depressed panel face. Therefore, thesuspension arm mounting member can be provided closer to the inside inthe vehicle width direction, so that the length of the suspension armcan be increased. Also, even if the suspension arm mounting member isprovided closer to the inside in the vehicle width direction, theattachment position does not lower, and a downward offset with respectto the vehicle body side attachment portion does not increase, so thatthe height from the road surface can be secured.

[0021] Further, according to another mode of the present invention, thelongitudinal position of the panel face on which the suspension armmounting member is installed is substantially aligned with the positionof the rear cross member.

[0022] In still another mode of the present invention, the suspensionarm mounting member and the panel face of the lower panel located on therear side of the mounting member are connected to each other by thefirst reinforcing member. Also, in still another mode of the presentinvention, the panel face of the lower panel located on the rear side ofthe suspension arm mounting member and the upper panel are connectedlongitudinally to each other by the second reinforcing member.

[0023] Therefore, the impact load imposed on the suspension arm mountingmember is also distributed to the first and second reinforcing members,so that the strength of the subframe body is further increased.

[0024] Further, in still another mode of the present invention, as thefirst reinforcing member, the rod-like or plate-like tie down hook canbe used. Although the tie down hook is usually used to fix a vehicle atthe time of transportation of vehicle, the tie down hook can be usedeffectively as the first reinforcing member.

[0025] In still another mode of the present invention, as the secondreinforcing member, the cylindrical reinforcing pipe can be used. Thecylindrical reinforcing pipe is arranged so that the axis thereof issubstantially aligned with the centers of the mounting holes in the reararm bracket. Therefore, an attaching bolt, a washer, and a tool such asa socket wrench are passed through the inside diameter of thereinforcing pipe to efficiently perform work for installing thesuspension arm to the mounting member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a plan view showing a subframe having a construction inaccordance with the present invention;

[0027]FIG. 2 is a perspective view of the subframe shown in FIG. 1, thesubframe being viewed from the slant front side;

[0028]FIG. 3 is a sectional view taken along the line A-A of FIG. 1;

[0029]FIG. 4 is a sectional view taken along the line B-B of FIG. 1;

[0030]FIG. 5 is a sectional view taken along the line C-C of FIG. 1;

[0031]FIG. 6 is a perspective view of the subframe shown in FIG. 1, thesubframe being viewed from the slant rear side;

[0032]FIG. 7 is a sectional view of the rear inside of a subframe inaccordance with the present invention;

[0033]FIG. 8 is a sectional view of the rear corner portion of asubframe in accordance with the present invention;

[0034]FIG. 9 is an exploded perspective view of a subframe body inaccordance with the present invention;

[0035]FIG. 10 is an exploded perspective view of a subframe body inaccordance with the present invention;

[0036]FIG. 11 is a conceptual view showing a state in which a load isapplied to a subframe in accordance with the present invention by afront collision;

[0037]FIG. 12 is a perspective view showing a modification of a tie downhook; and

[0038]FIG. 13 is a sectional view of a subframe having a conventionalconstruction.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0039] An embodiment of the present invention will now be described indetail with reference to the accompanying drawings.

[0040] As shown in FIG. 1, at the front part of a vehicle body, a frontcross member 1 and a rear cross member 3 are disposed in the vehiclewidth direction, and subframe bodies 5 are provided in the longitudinaldirection to connect the end portions 1 a and 3 a of these cross members1 and 3 to each other. The front cross member 1, the rear cross member3, and the subframe bodies 5 constitute a subframe 7 substantiallyhaving a shape of parallel crosses. At the end of the front cross member1 is provided a vehicle body mounting bracket 9 that is also used as anupper arm bracket. The rear cross member 3 is disposed at almost thesame position as the longitudinal position of a rear arm bracket 11.

[0041]FIG. 2 is a perspective view showing a state in which a suspensionarm 13 is disposed on the subframe body 5 and the front cross member 1,which are shown in FIG. 1, the view being taken from the slant frontside of a vehicle body. A rear-side arm 15 of the suspension arm 13 isinstalled to the rear arm bracket 11 disposed under the subframe body 5,and a front-side arm 19 of the suspension arm 13 is supported on thefront cross member 1 via a front arm bracket 17.

[0042] As shown in FIGS. 3 to 6, the subframe body 5 is formed byjoining peripheral portions 31 a and 33 a of an upper panel 31 and alower panel 33 to each other, and a hollow portion 35 of a closed crosssection construction is formed by the upper panel 31 and the lower panel33. Also, the cylindrical rear cross member 3 is disposed on the insidein the vehicle width direction of the subframe body 5, and the rear armbracket 11 is disposed on the face on the lower side and on the outsidein the vehicle width direction of the lower panel 33. As shown in FIG.4, a reinforcing pipe 43 is arranged so that the axis thereof passessubstantially through the centers of mounting holes in the rear armbracket 11.

[0043] As shown in FIG. 7, the upper panel 31 in accordance with thepresent invention has almost the same shape as that of the conventionalone, and the lower panel 33 has a lower face 37 formed by depressing alower side portion of a conventional lower panel 105 (indicated bytwo-dot chain lines) toward the inside in the vehicle width direction.Specifically, although the cross-sectional shape of a hollow portion ofa conventional subframe body is substantially a parallelogram, thesubframe body 5 in accordance with the present invention has the hollowportion 35 formed so as to have a substantially chevron shape in crosssection by depressing the lower side portion of the conventional lowerpanel 105.

[0044] The rear arm bracket 11 is installed on the rear side of thesubframe body 5. FIG. 8 is a perspective view in which a portion inwhich the rear arm bracket 11 is installed is cut. As shown in FIG. 8,the rear part of the subframe body 5 is formed substantially into aspherical shell shape which is formed by dividing a hemisphere openingdownward into about one-fourth and whose front side and outside in thevehicle width direction are open. To the rear end face of the lowerpanel 33 is joined a rear end portion 39 a of a tie down hook 39 formedinto a rod form by arc welding or other means. The rear arm bracket 11is joined to the face on the inside in the vehicle width direction ofthe lower panel 33, and a front end portion 39 b of the tie down hook 39is joined to a rear face 41 of the rear arm bracket 11.

[0045] The following is a description of an example of a procedure forconstructing the subframe body 5.

[0046] As shown in FIGS. 9 and 10, the peripheral portions 33a and 31 aof the lower panel 33 and the upper panel 31 are joined to each other.At this time, the rear cross member 3 is disposed on the inside in thevehicle width direction, and the reinforcing pipe 43 is provided betweenthe lower panel 33 and the upper panel 31. The rear arm bracket 11 isinstalled from the lower side of the lower panel 33, and the tie downhook 39 is installed so as to connect the rear arm bracket 11 to thelower panel 33, by which the subframe 7 shown in FIG. 6 can beconstructed.

[0047] Next, the operation of the subframe construction for a frontsuspension will be explained.

[0048] On a vehicle provided with the subframe 7 constructed asdescribed above, when a load is applied to a front tire, a load imposedon the subframe 7 can be distributed effectively.

[0049] Specifically, as shown in FIG. 11, an impact load F applied to afront tire 45 is first imposed on an attachment point 47 of thesuspension arm 13. The load is transmitted from the attachment point 47to the rear arm bracket 11 via the suspension arm 13. This load G actsin the direction of about 45 degrees with respect to the subframe body 5as shown in FIG. 11. Since the rear side and the inside in the vehiclewidth direction of the subframe body 5 is formed substantially into aspherical shell shape as explained with reference to FIG. 8, the load Gapplied to the rear arm bracket 11 can be taken by the subframe body 5while being distributed uniformly. Also, part of the load G is alsoapplied to the tie down hook 39 fixed to the rear arm bracket 11 and thereinforcing pipe 43 connecting the upper panel 31 and the lower panel 33to each other so that the load G is distributed. Therefore, the strengthof the subframe 7 can be increased as a whole.

[0050] Also, since the lower part of the lower panel 33 is depressedtoward the inside in the vehicle width direction, and thus the rear armbracket 11 can be installed at a position closer to the inside in thevehicle width direction, the length of the suspension arm 13 can beincreased. Further, even when the rear arm bracket 11 is located closerto the inside in the vehicle width direction, the height from the roadsurface is not changed, so that a downward offset with respect to thevehicle body side attachment portion does not increase. Also, since thereinforcing pipe 43 is disposed longitudinally at the rear of the reararm bracket 11, and the axis of the reinforcing pipe 43 is substantiallyaligned with the centers of the mounting holes 12 in the rear armbracket 11, a socket wrench extension can be passed through the insidediameter face of the reinforcing pipe 43.

[0051] The present invention is not limited to the above-describedembodiment, and various changes and modifications can be made based onthe technical concept of the present invention.

[0052] For example, the tie down hook 39 is not limited to a rod-likeone as shown in FIGS. 9 and 10, and may be a bracket-like one as shownin FIG. 12. This bracket-like tie down hook 49 is constructed of aplate-like body face 51 disposed vertically and a mounting flange 52formed by bending the upper edge of the body face 51 to the side, and atransversely elongated hook hole 53 is formed in the body face 51.

[0053] By changing the plate thickness and material of the tie down hook49, resistance to rearward movement of the front tire 45 caused by animpact from the front can be adjusted. Specifically, the center of therear cross member 3 and the center of the rear arm bracket 11 shiftslightly from each other in the vertical direction, so that the momentsuch as to warp the central portion of the rear cross member 11 upwardis produced.

1. A subframe construction for a front suspension, comprising a frontcross member disposed in the vehicle width direction at the front partof a vehicle body; a rear cross member disposed in the vehicle widthdirection on the rear side of said front cross member; a pair of rightand left subframe bodies for connecting these cross members to eachother, said subframe body having an upper panel and a lower panelforming a hollow portion therebetween; and a suspension arm mountingmember installed to the rear side on the outside in the vehicle widthdirection of said lower panel constituting said subframe body, whereinthe panel shapes of said upper panel and lower panel ranging from thelower panel face on which said suspension arm mounting member is mountedon said lower panel to the rear side of said lower panel are formedsubstantially into a spherical shell shape.
 2. The subframe constructionfor a front suspension according to claim 1, wherein a lower sideportion of the mounting face of said lower panel formed substantiallyinto a spherical shell shape is depressed toward the inside in thevehicle width direction, and said suspension arm mounting member isinstalled on the depressed panel face.
 3. The subframe construction fora front suspension according to claim 1 or 2, wherein the longitudinalposition of the panel face on which said suspension arm mounting memberis installed is substantially aligned with the position of said rearcross member.
 4. The subframe construction for a front suspensionaccording to any one of claims 1 to 3, wherein said suspension armmounting member and the panel face of said lower panel located on therear side of said mounting member are connected to each other by a firstreinforcing member.
 5. The subframe construction for a front suspensionaccording to any one of claims 1 to 4, wherein the panel face of saidlower panel located on the rear side of said suspension arm mountingmember and said upper panel are connected longitudinally to each otherby a second reinforcing member.
 6. The subframe construction for a frontsuspension according to any one of claims 1 to 5, wherein said firstreinforcing member is a rod-like or plate-like tie down hook.
 7. Thesubframe construction for a front suspension according to any one ofclaims 1 to 6, wherein said second reinforcing member is a cylindricalreinforcing pipe.